Methods of filling a liquid-filled lens mechanism

ABSTRACT

Methods for filling an internal volume of a liquid filled lens mechanism with fluid are provided. In some embodiments, the methods include creating a vacuum within the internal volume, de-aerating the fluid, filling the vacuum in the internal volume with the de-aerated fluid, and sealing the internal volume. In some embodiments, the methods include elevating a temperature of the fluid prior to sealing the internal volume. In some embodiments, the internal volume is formed by a structure having at least one flexible component.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/399,368, filed on Mar. 6, 2009, now U.S. Pat. No. 8,087,778, which isa continuation-in-part of U.S. patent application Ser. No. 12/370,938,filed on Feb. 13, 2009, now abandoned.

FIELD OF THE INVENTION

The present invention relates to the field of variable focus lenses, andmore particularly to consumer ophthalmic lenses that are at least inpart fluid- or liquid-filled.

BACKGROUND OF THE INVENTION

It is known that the ability of the human eye to accommodate, i.e., toalter the focal length of the natural lens in the eye, is graduallydiminished with increased age. Accommodation in human beings is reducedto 3D (diopters) or less at an age range of 35-45 years. At that point,reading glasses or some other form of near vision correction becomesnecessary for the human eye to be able to bring near objects (such aslines of text in a book or a magazine) to focus. With, further aging,accommodation drops below 2D, and at that point visual correction whenworking on a computer or when performing some visual task atintermediate distances is needed.

For best results and for best visual comfort, it is necessary to bringeach eye to focus on the same viewing target, e.g., a computer screen. Alarge segment of population requires a different visual correction foreach eye. These people, known as anisometropes, require different visualcorrection for each eye in order to achieve maximum visual comfort whilereading or working on a computer. It is known that, if each of the twoeyes of anisometropes is not brought to focus at the same viewing plane,the resulting anisometropic image blur causes a loss of stereopsis(depth perception). Loss of stereopsis is one of the best indications ofloss of binocular function. Loss of binocularity at the reading planemay cause a drop in reading speed and rate of comprehension, and mayhasten the onset of fatigue upon sustained reading or working on acomputer. Reading glasses fitted with individually adjustable liquidlenses are therefore uniquely suited for the visual need of individualswith loss of binocular function.

Variable focus lenses can take the form of a volume of liquid enclosedbetween flexible, transparent sheets. Typically, two such sheets, oneforming the lens front surface and one fowling the lens back surface,are attached to one another at their edges, either directly or to acarrier between the sheets, to form a sealed chamber containing thefluid. Both sheets can be flexible, or one can be flexible and onerigid. Fluid can be introduced into or removed from the chamber to varyits volume, and, as the volume of liquid changes, so does the curvatureof the sheet(s), and thus the power of the lens. Liquid lenses are,therefore, especially well suited for use in reading glasses, that is,eye glasses used by presbyopes for reading.

Variable focus liquid lenses have been known at least since 1958 (see,e.g., U.S. Pat. No. 2,836,101, to de Swart). More recent examples may befound in Tang et al, “Dynamically Reconfigurable Liquid Core LiquidCladding Lens in a Microfluidic Channel”, LAB ON A CHIP, Vol. 8; No. 3,pp. 395-401 (2008), and in International Patent Application PublicationNo. WO 2008/063442, entitled “Liquid Lenses with Polycyclic Alkanes”.These liquid lenses are typically directed towards photonics, digitalphone and camera technology, and microelectronics.

Liquid lenses have also been proposed for consumer ophthalmicapplications. See for example, U.S. Pat. No. 5,684,637 and U.S. Pat. No.6,715,876 to Floyd, and U.S. Pat. No. 7,085,065, to Silver. Thesereferences teach pumping of liquid in or out the lens chamber to changethe curvature of an elastic membrane surface, thus tuning the focus ofthe liquid lens. For example, U.S. Pat. No. 7,085,065, entitled“Variable Focus Optical Apparatus”, teaches a variable focus lens formedfrom a fluid envelope comprising two sheets, at least one of which isflexible. The flexible sheet is retained in place between two rings,which are directly secured together, such as by adhesive, ultrasonicwelding or any similar process, and the other, rigid sheet may bedirectly secured to one of the rings. A hole is drilled through theassembled lens to allow the cavity between the flexible membrane and therigid sheet to be filled with transparent fluid.

Liquid lenses have many advantages, including a wide dynamic range, theability to provide adaptive correction, robustness and low cost.However, in all cases, the advantages of liquid lenses must be balancedagainst its disadvantages, such as limitations in aperture size,possibility of leakage and inconsistency in performance. In particular,Silver has disclosed several improvements and embodiments directedtowards effective containment of the fluid in the liquid lens to be usedin ophthalmic applications, although not limited to them (e.g., U.S.Pat. No. 6,618,208 to Silver, and references therein). Power adjustmentin liquid lenses has been effected by injecting additional fluid into alens cavity, by electrowetting, by application of ultrasonic impulse andby utilizing swelling forces in a cross linked polymer upon introductionof a swelling agent such as water.

Commercialization of liquid lenses is expected to occur in the nearfuture, provided that some of the limitations noted above can beremedied. Even so, the structure of prior art liquid lenses is bulky andnot aesthetically suitable for consumers, who desire spectacles havingthinner lenses and spectacles without bulky frames. For the lenses thatoperate by injection or pumping of liquid into the body of the lens, acomplicated control system is usually needed, making such lenses bulky,expensive and sensitive to vibration.

In addition, to date, none of the prior art liquid lenses provides theconsumer with the ability to introduce the liquid into or remove it fromthe lens chamber so as to himself change its volume in order to vary thepower of the lens. In addition, none of the prior art liquid lensesprovides a mechanism to allow the consumer to introduce the liquid intoor remove it from the lens chamber so as to himself change its volume inorder to vary the power of the lens.

SUMMARY OF THE INVENTION

Methods for filling an internal volume of a liquid filled lens mechanismwith fluid are provided. In some embodiments, the methods includecreating a vacuum within the internal volume, de-aerating the fluid,filling the vacuum in the internal volume with the de-aerated fluid, andsealing the internal volume. In some embodiments, the methods includeelevating a temperature of the fluid prior to sealing the internalvolume. In some embodiments, the internal volume is formed by astructure having at least one flexible component.

The present invention will be better understood by reference to thefollowing detailed discussion of specific embodiments and the attachedfigures, which illustrate and exemplify such embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be understood and appreciated morefully from the following detailed description in conjunction with thefigures, which are not to scale, in which like reference numeralsindicate corresponding, analogous or similar elements, and in which:

FIG. 1A is a schematic cross-sectional view of a first embodiment of aliquid filled lens for use in spectacles or the like;

FIG. 1B is a schematic cross-sectional view of a second embodiment of aliquid filled lens for use in spectacles or the like;

FIG. 2 is an exploded schematic cross-sectional view of an embodiment ofthe spectacles apparatus utilizing the liquid filled lens;

FIGS. 3A and 3B show back and front perspective views of one half of anembodiment of the spectacles apparatus utilizing the liquid filled lens;

FIG. 4A is an exploded perspective view of the components of anembodiment of the spectacles apparatus utilizing the variable focus lensmechanism before introduction of fluid into the mechanism;

FIG. 4B is an exploded cross-sectional view of the components of anembodiment of the spectacles apparatus utilizing the variable focus lensmechanism before introduction of fluid into the mechanism;

FIG. 5A is a cross-sectional view of an embodiment of the variable focuslens mechanism within the spectacles apparatus before introduction offluid into the mechanism;

FIG. 5B is a cross-sectional view of an embodiment of the variable focuslens mechanism within the spectacles apparatus after introduction offluid into the mechanism;

FIGS. 6A and 6B are graphical software analyses of the performance ofthe liquid filled lens; and

FIGS. 7A and 7B are graphical software analyses of the performance ofthe liquid filled lens.

DETAILED DESCRIPTION OF THE INVENTION

The following preferred embodiments as exemplified by the drawings areillustrative of the invention and are not intended to limit theinvention as encompassed by the claims of this application.

FIG. 1A shows a cross-sectional view of a first preferred embodiment ofthe optical apparatus, in the form of a variable focus lens 10, throughwhich a wearer peers in the direction of arrow A. Lens 10 is a compositeof two optic components, an anterior (i.e., front, with respect to thewearer) optic 11 that is substantially rigid and a posterior (i.e.,back, with respect to the wearer) optic 15 that is a liquid.

Anterior optic 11 is a substantially rigid lens preferably made of arigid, transparent substrate, such as a clear plastic or poly carbonate,glass plate, transparent crystal plate, or a transparent rigid polymer,for example, Polycarbonate of Bisphenol A or CR-39 (Diethylene glycolbisallyl carbonate). Anterior optic 11 may be made of an impactresistant polymer and may have a scratch resistant coating or anantireflective coating.

In a preferred embodiment, anterior optic 11 has a meniscus shape, i.e.,convex at its front side and concave at its back side. Thus, both thefront and the back surfaces of anterior optic 11 are curved in the samedirection. However, as in all lenses that correct presbyopia (inabilityto accommodate), anterior optic 11 is thicker in the center and thinnerat the edge, i.e., the radius of curvature of the front surface ofanterior optic 11 is smaller than the radius of curvature of the backsurface of anterior optic 11, such that the respective radii ofcurvature of the front and the back surfaces of anterior optic 11, andhence the front and the back surfaces themselves, intersect. Theintersection of the front and the back surfaces of anterior optic 11 isthe circumferential edge 16 of anterior optic 11.

In certain embodiments, the front surface of anterior optic 11 isspherical, meaning it has the same curve across its entire surface, asin conventional eyeglasses lenses. In a preferred embodiment, anterioroptic 11 is aspheric and has a more complex front surface curvature thatgradually changes from the center of the lens out to the edge, so as toprovide a slimmer profile and a desired power profile as a function ofthe gaze angle, the gaze angle being defined herein as the angle formedbetween the actual line of sight and the principal axis of the lens.

Posterior optic 15 is a liquid lens composed of a fluid 14. Fluid 14 isconfined within a cavity formed between the back surface of the anterioroptic 11 and a membrane 13 that is attached to the edges of anterioroptic 11. Membrane 13 is preferably made of a flexible, transparent,water impermeable material, such as clear and elastic polyolefins,polycycloaliphatics, polyethers, polyesters, polyimides andpolyurethanes, for example, polyvinylidene chloride films, includingcommercially available films, such as those manufactured as Mylar® orSaran®. It has been found that a proprietary clear transparent film madeof Polyethylene terephthalate is one preferred choice for the membrane.

The cavity between the back surface of the anterior optic 11 and amembrane 13 in FIG. 1A is formed by sealing membrane 13 to the peripheryor circumferential edge 16 of the anterior optic 11. Membrane 13 may besealed to anterior optic 11 by any known method, such as heat sealing,adhesive sealing or laser welding. Membrane 13 can be is at least inpart bonded to a support element that is in turn bonded to the peripheryof anterior optic 11. Membrane 13 is preferably flat when sealed but maybe thermoformed to a specific curvature or spherical geometry.

Fluid 14 encapsulated between membrane 13 and the back surface of theanterior optic 11 is preferably colorless. However, fluid 14 can betinted, depending on the application, such as if the intendedapplication is for sunglasses. Fluid 14 having an appropriate index ofrefraction and viscosity suitable for use in fluid filled lenses, suchas, for example, degassed water, mineral oil, glycerin and siliconeproducts, among others that are commonly known or used for fluid filledlenses. One preferred fluid 14 is manufactured by Dow Corning® under thename 704 diffusion pump oil, also generally referred to as silicone oil.

In certain embodiments, membrane 13 by itself has no constraints in itsoptical properties. In other embodiments, membrane 13 has constraints inits optical properties, e.g., an index of refraction, that match theoptical properties of fluid 14.

In use, at least one lens 10 is fit within a set of eyeglass orspectacle fumes for use by a wearer. As shown in FIG. 1A, in profile,lens 10 allows the user to see through both anterior optic 11 andposterior optic 15, which together provide a thicker profile at thecenter of lens 10, and stronger presbyopic visual correction, than justanterior optic 11. The wearer is provided with the ability to adjust theamount of fluid 14 within posterior optic 15 and thereby adjust therefractive power of lens 10. In certain embodiments, as will bediscussed below, the frame is equipped with a reservoir of excess fluid14 and a fluid line communicating the reservoir to the posterior optic15 of lens 10. The spectacles frame also preferably has an adjustmentmechanism to allow the wearer to personally adjust the amount of fluid14 within posterior optic 15 so that fluid 14 that can be moved into orexpelled from the reservoir into the posterior optic 15 to therebyadjust the refractive power of lens 10 as needed.

FIG. 1B shows a cross-sectional view of a second preferred embodiment ofthe optical apparatus, in the form of a variable focus lens 20, throughwhich a wearer gazes in the direction of arrow A. As opposed to lens 10in FIG. 1A, which is a composite of two optic components, lens 20 inFIG. 1B is a composite of three optic components, namely, an anterioroptic 21 that is substantially rigid, an intermediate optic 25 that is aliquid and a posterior optic 35 that is a liquid.

Anterior optic 21 is a substantially rigid lens, similar in structureand design to that of anterior optic 11 of the embodiment shown in FIG.1A. As in anterior optic 11 of FIG. 1A, anterior optic 21 also has ameniscus shape, i.e., both the front and the back surfaces of anterioroptic 11 are curved in the same direction, and the radius of curvatureof the front surface of anterior optic 21 is smaller than the radius ofcurvature of the back surface of anterior optic 21, such that theintersection of the front and the back surfaces of anterior optic 21 isthe circumferential edge 26 of anterior optic 21. However, the radius ofcurvature of the back surface of anterior optic 21 is larger than theradius of curvature of the back surface of anterior optic 11 of FIG. 1A.Similarly, as compared to anterior optic 11 of FIG. 1A, anterior optic21 may be somewhat thinner than anterior optic 11 of FIG. 1A, so as tomaintain the same general overall thickness of lens 20 as compared tolens 10 of FIG. 1A.

Intermediate optic 25 is a liquid lens composed of a fluid 24, similarto fluid 13 as described with respect to FIG. 1A, that is confinedwithin a cavity formed between the back surface of the anterior optic 21and a membrane 23 that is attached to the edges 26 of anterior optic 21and is similar in structure and design to that of membrane 13 of theembodiment shown in FIG. 1A. Fluid 24 has a selected refractive index(n₂₃).

It is preferred that intermediate optic 25 also have a meniscus shape,such that both its front and back surfaces are curved in the samedirection. Naturally, the back surface of rigid anterior optic 21 may beformed with a curvature during manufacture. However, the concavecurvature of membrane 23 may be accomplished by thermoforming it to aspecific curvature or spherical geometry when it is being sealed to theedges 26 of anterior optic 21. This may be accomplished by a reducingthe pressure within the sealed cavity formed between membrane 23 and theback surface of anterior optic 21. Thus, the radius of curvature of theback surface of anterior optic 21 is smaller than the radius ofcurvature of the membrane 23, and the intersection of the back surfaceof anterior optic 21 and membrane 23 is the circumferential edge 26 ofanterior optic 21.

Posterior optic 35 is a liquid lens composed of a fluid 34, similar tofluid 13 as described with respect to FIG. 1A, that is confined within acavity formed between membrane 23 and a membrane 33. Fluid 34 has aselected refractive index (n₃₄).

Membrane 33 has similar in structure and design to that of membrane 13described regarding the embodiment shown in FIG. 1A. Membrane 33 mayalso be attached to the edges 26 of anterior optic 21 but posterior to,or over the edges of, the attached membrane 23. Alternatively, one ormore rings, or half-rings, may be used to provide a seat for sealingmembrane 23 and membrane 33.

Membrane 33 is preferably flat when sealed but may be thermoformed to aspecific curvature or spherical geometry. In preferred embodiments, thepositive pressure within intermediate optic 25 is lower than thepositive pressure within posterior optic 35. The greater positivepressure within posterior optic 35 controls the shape of membrane 23 andthe respective refractive powers of intermediate optic 25 within thecavity between the back surface of anterior optic 21 and membrane 23 andof posterior optic 35 within the cavity between membrane 23 and membrane33.

In use, at least one lens 20 is fit within a set of eyeglass orspectacle frames designed for ophthalmic applications for use by awearer. As shown in FIG. 1B, in profile, lens 20 allows the user to seethrough all of anterior optic 21, intermediate optic 25 and posterioroptic 35, which together provide a thicker profile at the center of lens20, and stronger presbyopic visual correction, than just anterior optic21. In certain embodiments, the wearer is provided with the ability toadjust the amount of fluid 24 within intermediate optic 25 or the amountof fluid 34 within posterior optic 35, or within both, and therebyadjust the refractive power of lens 20. In certain embodiments, as willbe discussed below, the frame is equipped with a reservoir of fluid 24or a reservoir of fluid 34, or both, and a fluid line connecting therespective reservoir to the intermediate optic 25 or the posterior optic35 of lens 20. The spectacles frame also preferably has one or moreactuators or adjustment mechanisms to allow the wearer to personallyadjust the amount of fluid 24 and fluid 34 within intermediate optic 25and posterior optic 35, respectively, so that fluid 24 and fluid 34 thatcan be moved into or expelled from the respective reservoir into theintermediate optic 25 and the posterior optic 35, and thereby adjust therefractive power of lens 20 as needed.

Other embodiments of the optical apparatus having even more opticalcomponents are also possible. In addition to lens 10 in FIG. 1A, whichis a composite of one rigid optic and one liquid optic, and lens 20 inFIG. 1B, which is a composite of one rigid optic and two liquid optics,the optical apparatus can also be a composite of one rigid optic andmore than two liquid optics. Such embodiments, which are not shown here,may provide advantages to the user and may allow more refined andsophisticated ophthalmic adjustment than the embodiments described inFIGS. 1A and 1B.

Accordingly, in preferred embodiments, lens 10 or 20 may be used forapplications in eyeglasses. Preferably, the lenses 10 or 20 for the leftand the right eye are designed independently and are capable ofadjustment of each eyeglass lens separately by the wearer. In such acase, it is preferred that a separate liquid reservoir be in fluidcommunication with each lens, i.e., connected to it by its own liquidline. In its most preferred embodiment, the liquid lens assembly,comprising the liquid lens, the reservoir and said liquid togetherconstitute a sealed system, thus minimizing incursion of water orevaporation or leakage of the liquid. The fluid is driven by some forcegenerated by a user when an adjustment in power is desired, and is thusbe moved into or expelled from the respective reservoir into the fluidoptic. The mechanism of adjustment of power of the liquid lens is bymeans of liquid transfer between the cavity and a reservoir.

FIG. 2 shows an exploded schematic cross-sectional view of an embodimentof eyeglasses or spectacles 1 utilizing the liquid filled lens.Spectacles 1 has a frame or lens support 5, within which the variablefocus lens is seated. For simplicity, FIG. 2 shows only one (the left)side of a set of spectacles having two eyeglasses, i.e., one for eacheye. In addition, FIG. 2 shows a variable focus lens having only onefluid optic, e.g., as in lens 10 of FIG. 1A. For simplicity, variousembodiments of the spectacles are described herein with respect to theembodiment of lens 10 having one fluid optic. Anterior optic 1 andmembrane 13 are seen in the exploded view of FIG. 2, and one reservoir6, which in fluid communication with the cavity formed between anterioroptic 1 and membrane 13, is shown.

Similarly, FIGS. 3A and 3B show back and front perspective views of theleft eyeglass portion of an embodiment of the spectacles apparatus 1design for ophthalmic application utilizing the liquid filled lens. Theeyeglass portion in FIGS. 3A and 3B consists of a frame 5 for supportinglens 10 and a temple piece 4. If the right eyeglass of the user alsorequires ophthalmic adjustment, then the right eyeglass would besubstantially a mirror image of the left side. The lenses 10 or 20 forthe left and the right eye are designed independently, since the pointof attachment of the liquid lenses to the reservoir(s) may be mirrorimages to each other.

Anterior optic 11 and membrane 13 are seen in the exploded view of FIG.2, and one reservoir 6, which in fluid communication with the cavityformed between anterior optic 1 and membrane 13, is shown. As shown ingreater detail in FIGS. 3A, 3B, 4A and 4B, the components of liquidfilled lens 10, namely anterior optic 11 and membrane 13, as well asring 8 in which they are mounted, are shown. Reservoir 6, situated insome embodiments attached to or in frame 5, has a hollow cavitycontaining extra fluid 14 that can be injected into lens 10 through thefluid communication channel. The extra fluid 14 within reservoir 6preferably does not completely fill reservoir 6 so as to allowadditional fluid 14 from lens 10 to be drawn into reservoir 6.

As shown in FIGS. 3A and 3B, reservoir 6 has a mechanism or actuator 7to inject fluid 14 into or draw fluid 14 out of the liquid lens optic15. In one embodiment, reservoir 6 is made of a rigid material, and isfitted with a piston that is mechanically coupled to an adjustmentmechanism or actuator 7, such as a thumb wheel, a barrel, a clamp or alever, that may be attached to the lens holder frame 5 or to theeyeglasses temple piece 4. In the embodiment wherein actuator 7 is abarrel that is situated coaxially with the temple piece 4, as shown inFIGS. 4A and 4B, fluid may be forced out of reservoir 6, through thefluid channel and into lens 10 by turning the barrel actuator 7. Incertain embodiments, once the optical power of lens 10 is adjusted bythe actuator 7, the actuator 7 may be altered or disabled to preventfurther adjustment of the optical properties of lens 10 by the wearer.

FIGS. 4A and 4B are exploded perspective and cross-sectional views thatshow in greater detail the components of the left eyeglass and frame ofan embodiment of the spectacles assembly utilizing the variable focuslens mechanism, before introduction of fluid into the mechanism. Lens 10is formed, as shown in FIG. 1A, by anterior optic 11 and membrane 13,and posterior optic 15 of lens 10 is in fluid communication withreservoir 6, which is shown as a hollow well that can retain fluid 14.

Reservoir 6 is in fluid communication with the cavity of lens 10, i.e.,posterior optic 15, and injects fluid 14 into posterior optic 15 througha fluid channel 31, which may be any tube or passageway that connectsreservoir 6 to the cavity of lens 10. Such a fluid channel 31 may be ashort tube that extends the shortest possible distance from reservoir 6to posterior optic 15. However, due to the viscosity of fluid 14, afluid channel having only one entry point into posterior optic 15 islikely to restrict the flow of fluid 14 from reservoir 6 to posterioroptic 15 and thus the time to effect the desired ophthalmic change. Evenif such a fluid channel 31 were sufficiently wide such that fluid 14flows sufficiently quickly, having one only entry point into posterioroptic 15 might not enable fluid 14 to be evenly distributed withinposterior optic 15 sufficiently quickly so as to effect the desiredophthalmic change with the desired speed.

In one preferred embodiment, fluid channel 31 has more than one point ofinjection of fluid 14 into posterior optic 15. In one embodiment, thefluid channel 31 that provides the fluid communication between reservoir6 and posterior optic 15 may be in the form of a hollow ring 8, aspreviously described. The ring 8 may define a fluid channel, in the formof a hollow space inside ring 8. In one embodiment, ring 8, which may beset within the lens support or frame 5, as shown in. FIG. 4B, may beprovided with a series of radial holes or openings arranged along theinside surface of ring 8 and through which the liquid is injected intoposterior lens 15. The radial holes are preferably spaced at regularintervals, or more preferably at the most optimal distances from oneanother so as to deliver fluid 15 at a controlled rate. In certainembodiments, ring 8 does not extend completely around lens 10, but only,for example, around the top portion of lens 10. This may be done forstylistic reasons, e.g., so as not to require the user to wear aheavy-looking frame. In such an embodiment, the radial holes arearranged along the inside surface of that portion of ring 8 so as toinject fluid 14 into lens 10 from its top edge only.

As shown in FIG. 4B, ring 8 may be in fluid communication with reservoir6 by means of a short liquid communication channel 31. In someembodiments, wherein spectacles 1 have more than one liquid optic, suchas in lens 20 of FIG. 1B, each liquid lens cavity could be provided witha unique reservoir 6, each in fluid communication with a respectivecavity of lens 20. Each liquid lens cavity could also be provided with aunique ring 8, so that the liquid channels remain separate for eachcavity.

In addition to providing a fluid communication to posterior optic 15,ring 8, as the seat of the sealed flexible membrane, performs theadditional function of providing a platform of defined width and tilt towhich membrane 13 is bonded. In one embodiment, the surface of ring 8 isellipsoidal in order to provide a stable planar seat for sealing ontoanterior optic 11 on one side and flexible membrane 13 on the other. Insuch an embodiment, in order to avoid leakage of fluid 14 from lens 10,ring 8 must be sealed to anterior optic 11 and to flexible membrane 13.The process of sealing ring 8 to anterior optic 11 and to flexiblemembrane 13 may involve use of an adhesive such as an epoxy adhesive ormay involve a welding process, including a laser welding process. Onepreferred method of laser welding sealing involves utilizing a laserabsorbing dye solution that is applied to the interface to effectpreferential absorption of laser energy at the interface. The preferredwidth of laser welding is between 0.5 and 2.0 mm, more preferably 1.0mm.

In one embodiment of spectacles 1, the diameter of lens 10 is about 39mm. However, because the edge of lens 10 may be utilized to form a bondbetween anterior optic 11 and membrane 13 or between the lens assembly10 and frame 5, the optically clear area will generally be somewhatless, e.g., about 35 mm. The ring 8 is 2.0 mm in outer diameter, and 1.0mm in inner diameter. The inner surface of the ring 8, i.e., facing thecavity, is provided with openings, e.g., 1 mm in diameter, disposedradially.

As shown in FIG. 4B, reservoir 6 is preferably covered and sealed with aflexible thermoplastic membrane 27. Membrane 27 may be made of Mylar®, apolyimide or a thermoplastic elastomer (TPE), preferably TPE. Membrane27 may be the same material as membrane 13. However, in certainembodiments, membrane 27 is preferably not the same material as membrane13, as membrane 27 need not be transparent.

In one embodiment, membrane 27 may be injection molded or thermoformedto fill the space inside reservoir 6. Membrane 27 may be joined orbonded to the inner surface of reservoir 6, such that membrane 27 bulgesout over the top of reservoir 6, like a cushion or a balloon, in themanner of a diaphragm. The details of this subassembly are more clearlyshown in FIGS. 5A and 5B. In another embodiment, membrane 27 may bejoined or bonded or form-fitted over the outer edges of reservoir 6.

Membrane 27 forms an air-tight and fluid-tight seal on reservoir 6. Incertain embodiments, membrane 27 projects upwards to form a bubble overthe top of reservoir 6. Typically, the total internal volume of all ofreservoir 6, liquid communication channel 31, ring 8 and posterior optic15 of lens 10 together forms a single sealed space, substantially filledwith fluid at all times. As the outward-bulging portion of membrane 27is pushed inward into reservoir 6, the volume within reservoir 6 isdecreased, such that membrane 27 creates positive pressure in reservoir6, pushing fluid 14 out of reservoir 6, through liquid communicationchannel 31 and ring 8, and into posterior optic 15 of lens 10.Similarly, as the outward-bulging portion of membrane 27 is pulledoutward from reservoir 6, the volume within reservoir 6 is increased,such that membrane 27 creates negative pressure in reservoir 6, pullingfluid 14 into reservoir 6, through liquid communication channel 31 andring 8, from posterior optic 15 of lens 10.

Membrane 27 can be pushed downwards into reservoir 6 or pulled upwardsaway from reservoir 6 by any known means using an actuator 7. By suchmotion of membrane 27, fluid 14 is thereby expelled from reservoir 6 orpulled into reservoir 6. Since change of the amount of fluid withinreservoir 6 will also change the amount of fluid 14 within lens 10, theoptical properties of lens 10 can be changed.

In the embodiment shown in FIGS. 4A and 4B, actuator 7 has a plunger 28situated immediately outside, and impinging against, membrane 27 and amovement device that provides movement to plunger 28. Movement ofplunger 28 in a direction towards membrane 27 increases pressure ontomembrane 27 and within reservoir 6, and movement of plunger 28 in adirection away from membrane 27 decreases pressure on membrane 27 andwithin reservoir 6. Plunger 28 is movable in opposing directionssubstantially transverse to membrane 27, and plunger 28 exerts pressureonto reservoir 6 by motion relative to membrane 27 due to a force orimpulse exerted on a movement device. The movement device can be anydevice, such as a screw, lever, slide mechanism, etc., that providescontrolled, adjustable and incremental movement to plunger 28.

In the embodiment shown in FIG. 4B, the movement device of actuator 7 isin the form of a barrel screw 29, which is threaded coaxially withtemple piece 4 on frame 5 and coaxially with plunger 28 so as to providemovement to plunger 28 in directions toward and away from membrane 27.The actuation of the movement device of actuator 7, namely the rotationof barrel screw 29 along its threads, in a first direction, movesplunger 28 inwards towards membrane 27, pushing membrane 27 inwards intoreservoir 6 and creating positive pressure inside reservoir 6. Thispositive pressure in reservoir 6 squeezes liquid 14 out of reservoir 6,through liquid communication channel 31 and ring 8, and into lens 10. Incertain embodiments, plunger 28 forces membrane 27 so far back insidereservoir 6 such that membrane 27 nearly touches the bottom of reservoir6.

Conversely, the actuation of the movement device of actuator 7, namelythe rotation of barrel screw 29 along its threads, in a directionopposite to the first direction, moves plunger 28 away from membrane 27,allowing membrane 27 to move outwards from reservoir 6 and creatingnegative pressure inside reservoir 6. This negative pressure inreservoir 6 pulls liquid 14 into reservoir 6, through liquidcommunication channel 31 and ring 8, from lens 10. By rotation of barrelscrew 29 in a first direction or in a direction opposite to the firstdirection, fluid 14 can be expelled from reservoir 6 into lens 10 or canbe sucked into reservoir 6 from lens 10, to thereby change the opticalproperties of lens 10.

Liquid transfer between reservoir 6 and the fluid filled cavity, i.e.,posterior optic 15 of lens 10, occurs through application of a force bymeans of the actuator 7. There is no universal need to prevent backflowof the fluid 14 from the cavity to the reservoir 6 since the whole fluidcompartment comprising the cavity 15, the reservoir 6 and the channel31/ring 8 is sealed and in communication with one another equalizing thepressure within. However, there may be a need to apply a unidirectionalpower correction for certain optical or visual needs. In such as case,actuator 7 may be made unidirectional, i.e., it only functions to moveplunger 28 in one direction, either to force liquid 14 into lens 10 orto pull liquid 14 out of lens 10. In such an embodiment, gears (notshown) may be employed to prevent actuator 7 from reversing its action.Actuator 7 is typically adjusted manually as the wearer's need foradditional ophthalmic power emerges. Alternatively, actuator 7 may beautomatically adjusted by application of an electrical, magnetic,acoustic or thermal force, triggered in response to signal from a sensorthat recognizes the need for additional power and sends a signal to thateffect.

The sealed internal volume of the single sealed space consisting ofreservoir 6, liquid communication channel 31, ring 8 and posterior optic15 of lens 10 must be filled prior to operation of spectacles 1. In oneembodiment, the internal volume is initially filled before sealing ofspectacles 1 by injecting fluid 14 at an elevated temperature (preferredrange 45-90° C., preferably 65-80° C.). Filling of the internal volumemay be done through one or more inlets, such as inlet 30A belowreservoir 6 or inlet 30B at the remote edge of ring 8, or both, as shownin FIGS. 4B and 5A. Filling of the internal volume is preferably doneunder vacuum, using freshly de-aerated fluid, so that a minimum of airis included within the sealed internal volume. In fact, it is preferredthat no air, i.e., a vacuum, be within the sealed internal volume suchthat operation of actuator 7 will move only fluid 14 into and out oflens 10. Once the spectacles assembly 1 is sealed, inlets 30A and 30Bmay be sealed off or removed, leaving no outlet for fluid 14 or air atthe locations of inlets 30A and 30B. FIG. 5A shows the spectaclesassembly before introduction of fluid into the mechanism, with inlets30A and 30B intact, and FIG. 5B shows spectacles assembly after fillingwith fluid and sealing, with inlets 30A and 30B sealed off.

The optical and mechanical design of the liquid lens enables its mainfunction, namely to provide capability to adjust optical power over asbroad a range as possible without significantly impacting cosmeticappearance, durability or optical performance. A goal of the design isto minimize the volume of the liquid lens 10, preferably by reducing itsthickness. The thickness of the liquid lens depends on the curve of theback surface of the anterior optic 11 and the diameter of the lenssystem. The dimensions of the liquid lens was designed using an FiniteElement Model (FEM) that accepts as input the surface geometry of theback surface of the anterior optic 11, the required adjustable powerrange, and the thickness of the fluid 14 layer when the membrane 13 isflat.

For example, in one embodiment, a liquid lens system covering the rangeof powers from 1.25 D to 3.25 D consists of the anterior optic 11 thatis of zero spherical power. The preferred range of the radius ofcurvature of the anterior optic 11 is between 100 to 700 mm depending onthe refractive index of the material used to fabricate anterior optic11, more preferably between 500 and 600 mm. The preferred range ofthickness of anterior optic 11 is 0.7 to 2.5 mm, more preferably between1.0 and 1.5 mm, and most preferably about 1.3 mm. It is well known thatspherical aberration that affects the effective power provided by anoptic away from its center, depends on the angle of gaze and the powerat the center. For an optic of 30-40 mm in diameter (that controls themaximum gaze angle) and for a paraxial power range of 1.0 D to 5.0 D,the off axis deviation in power is expected to be about 0.25-0.50 D.

The preferred embodiment of lens 10 (anterior optic 11 and posterioroptic 15) has a power equal to 1.21 D at the center, the liquid layer ofposterior optic 15 having a thickness of ranging from 0.7 to 1.5 mm atthe center, preferably 1.3 mm. The diameter of lens 10 is 35 mm, whilethe radius of curvature of membrane 13 is infinity, since membrane 13 isbonded flat. The total volume of fluid in the liquid lens isapproximately 1.35 mL, while an additional volume of 0.350 mL resides inthe reservoir.

The power of lens 10 increases when the pressure of liquid 14 inposterior optic 15 is increased by injecting more liquid 14 into thecavity from reservoir 6. The radius of curvature of membrane 13 is 274mm when the lens power reaches 3.25 D. 300 microliters (0.30 mL) offluid 14 is required to reach the level of positive pressure required tocause the required level of deformation (bulging) of membrane 13.

A mechanical finite element model (FEM) model was developed to predictthe pressure required to increase the power of the whole lens and theresulting displacement of membrane 13. The model was created for twothicknesses of membrane 13, 23 and 46 microns (1 and 2 mil), and forthree different values of tensile modulus of the membrane 13, namely 2.0GPa, 3.0 GPa and 4.0 GPa. FIGS. 6A and 6B show output from the FEM modelshowing pressure build up as a result of fluid injection into the liquidlens of the three preferred configurations.

FIGS. 6A and 6B show that membrane 13 undergoes elastic deformationleading to displacement of its center outwards as fluid is pumped in andpressure increases. It is clear that 2.0 D of power enhancement can beachieved well within the elastic range of deformation of this material.In fact, since the increase in power is approximately linear with thedisplacement of the center of the membrane at this range, the FEM modelpredicts that less than 1 mm of center displacement will lead to a 4 Dof power increase in the 38 mm optic, while the elastic limit is reachedonly when the displacement reaches 3 mm. Moreover, the shape of thedeformed membrane remains reasonably spherical over the whole of theelastic range.

A well known deficiency of liquid lenses or compound lensesincorporating a liquid lens component is that the fluid volume requiredfor a particular increase in power increases dramatically with opticdiameter. This phenomenon has limited the application of liquid lensesto optics of small apertures only, thus preventing its widespread use inophthalmic lens applications. This is borne out by the prediction madeby the FEM model (FIG. 7A), showing that there is a doubling of thevolume of fluid required to increase optical power by 2.0 D of abaseline power of 1.21 D if the optic diameter increases from 32 mm to38 mm. However, the volume is reduced by a factor of 2 as the radius ofthe front optic is increased from 260 mm to 500 mm. We have used the FEMmodel to obtain the optimum curvature of the front curve of the rigidoptic for the optic diameter required for a particular frame.

It is also necessary for membrane 13 to be under a minimum positivepressure in order to ensure a stable optical performance of a liquidlens. This positive pressure prevents development of wrinkles andprevents gravity-induced pooling of liquid 14 at the bottom of thecavity to affect the optical power. An FEM model was used to estimatethe minimum amount of positive pressure needed for stable operation evenwhen optical power is not enhanced through injection of additional fluidfrom the reservoir. FIGS. 7A and 7B show the results of the FEM model,showing the increase in fluid volume required in order to achieve aparticular increase in power: dependence on optic diameter and frontcurve radius in the preferred embodiment.

We determined through tests that the minimum pressure required toprevent wrinkles is about 3 millibar (mbar) for a 38 mm optic coveredwith a 23 micron thick Mylar membrane with a modulus of 3 GPa. Modelingof the gravitationally induced pooling effects showed that about 2 mbarof positive pressure will counteract the gravitational force. Inaddition, temperature variations will also alter the positive pressurebuilt into the liquid lens, and will affect the optical performance ofthe liquid lens. Based on these considerations, including modelpredictions and test results, it was decided that a positive pressure of10 mbar will be sufficient to ensure the membrane to remain stretchedover all use conditions. This amount of positive pressure can be inducedby reducing the baseline power below the required range of powervariations, or also by changing the thickness of the membrane. It wasdetermined that a membrane of thickness 200 microns and modulus 3 GPawill require a positive pressure of approximately 10 mbar for an opticdiameter of 38 mm in order to maintain a power increase of 0.25 D. Theenhanced thickness of the flexible membrane enhances its durability androbustness, without adding significantly to the overall lens thickness.

Thus, a mechanism for operating a liquid filled lens has been provided.One skilled in the art will appreciate that the present invention can bepracticed by other than the described embodiments, which are presentedfor purposes of illustration and not limitation, and that the inventionis limited only by the claims that follow.

What is claimed is:
 1. A method of filling an internal volume of aliquid filled lens mechanism with fluid, the method comprising: creatinga vacuum within the internal volume of the lens mechanism, the internalvolume including an internal portion of a liquid filled lens and areservoir; de-aerating the fluid; filling the vacuum in the internalvolume with the de-aerated fluid; and sealing the internal volume. 2.The method of claim 1, wherein de-aerating the fluid occurs beforecreating a vacuum within the internal volume.
 3. The method of claim 1,further comprising: elevating a temperature of the fluid prior tosealing the internal volume.
 4. The method of claim 3, wherein elevatingthe temperature of the fluid comprises elevating the temperature of thefluid to a range from about 45° C. to about 90° C.
 5. The method ofclaim 3, wherein elevating the temperature of the fluid compriseselevating the temperature of the fluid to a range from about 65° C. toabout 80° C.
 6. The method of claim 3, wherein de-aerating the fluidoccurs before elevating the temperature of the fluid.
 7. The method ofclaim 3, wherein de-aerating the fluid occurs at the same time aselevating the temperature of the fluid.
 8. The method of claim 1,wherein the fluid is silicone oil.
 9. The method of claim 1, wherein theinternal volume is formed by a structure having at least one flexiblecomponent.
 10. The method of claim 1, wherein filling the vacuum in theinternal volume comprises filling the internal volume with fluid throughan inlet in the liquid filled lens mechanism.
 11. The method of claim10, wherein sealing the internal volume comprises sealing off the inletafter filling the internal volume.
 12. The method of claim 10, whereinsealing the internal volume comprises removing the inlet after fillingthe internal volume.
 13. The method of claim 1, wherein filling thevacuum in the internal volume comprises filling the internal volume withfluid through a plurality of inlets in the liquid filled lens mechanism.